Conventionally, when using mold injection procedures in dies or molds, in order to let the melted plastic material be filled inside the dies and be flowed smoothly, and to prevent the melted plastic material from being cooled too early, a first die and a second die have to be pre-heated to a certain temperature before combining the two dies for injection procedures. This can prevent the melted plastic material from being cooled too prematurely and to allow the melted plastic material to flow smoothly before forming process.
Conventionally, injection-molding uses fixed type heating method inside a first and a second die, high frequency heating techniques may be applied. As shown FIG. 1, which is an invention “Instantly Pre-Heating Mold Structure for Fist and Second Dies” with Publication No. 463718. It uses a first and a second die, in which the first die includes a die contact part, a heating system and a cooling system by its side. The second die includes a die contact part and a filling hole by its side. A first and a second die surfaces are disposed on the heating and cooling system respectively. The first die surface is corresponding to a ceramic or cement epoxy enclosed high frequency induction heating coil system, which is slightly bigger than a die contact part groove, and is disposed at the back of the die contact part. Firstly, let the first die surface be pre-heated, then combine the first and the second die surfaces inside the second die, injection forming is completed speedily and will detach from the dies after being cooled down by a piping system of the cooling system inside the second die surface. The first die surface includes a small area for speedy pre-heating and the second die surface provides a simultaneous cooling effect for injection. Regardless of using either electrical heating or high frequency heating method, the heat must be distributed throughout the whole die in order to let the melted plastic material be flowed smoothly into the die hole for forming. Therefore, the drawback of this conventional type of pre-heating device disposed inside the dies is that, the time needed for pre-heating is long, especially the time needed for pre-heating the die contact part. Secondly, pre-heating temperature often cannot reach an ideal level in the die contact part, causes the melted plastic material unable to flow smoothly inside the dies hole for forming and thus increases the percentage of defective products. Thirdly, even the melted plastic material can flow smoothly inside the dies, the time needed for cooling is often too long and will affect the cooling effect for forming. Therefore, it is a priority to improve the pre-heating and cooling process effectiveness and to shorten the time.
As shown in FIG. 2, illustrated is an outer type dies pre-heating device. It mainly comprises a gas burner head, a fuel pipe, a supportive frame and a regulator valve. The gas burner head is formed on an upper and a lower parts of the dies pre-heating device, concave airing spaces are formed and provided on the upper and the lower parts of the dies pre-heating device. The gas burner head with evenly arranged holes is disposed on the inner ring of the concave airing spaces. The fuel pipe with its one end is screwed on the gas burner head, and another end is connected to a fuel tank to form a circulation body. The supportive frame with its one end is disposed on the middle part of the fuel pipe, and another end is disposed on a forging or injection-forming machine. The regulator valve is connected on an ideal location of the fuel pipe in order to open or close the passage from the fuel tank, and to adjust the fuel volume, so that the temperature can be pre-heated to a desired working temperature from room temperature for the processes of forge-molding and injection-molding of an upper and a lower dies of the forging or injection-molding machine. This conventional type pre-heating device can achieve the pre-heating effectiveness but is only suitable for large-sized forging or injection dies. Besides, it is not suitable for dies of precision parts.